Abstract:

Provided is a method of cleaning the inside of a pressure vessel for
blasting to enable a short-time treatment regardless of the state of
residual substances. This method includes: a step of setting an explosive
for cleaning, different from an explosive for blasting, in an amount
necessary for decomposing a residue of the object inside of a pressure
vessel after a blasting step of setting and blasting the object and the
explosive for blasting in the pressure vessel; and a step of decomposing
the residue by exploding the explosive for cleaning in the pressure
vessel.

Claims:

1. A method of cleaning the inside of a pressure vessel for blasting for
decomposing a residue of an object to be blasted in the pressure vessel
to clean it following a blasting step of setting the object and an
explosive for blasting in the pressure vessel and blasting them therein,
comprising:a setting step of setting an explosive for cleaning, different
from the object to be blasted, in an amount necessary for decomposing the
residue of the object to be blasted inside of the pressure vessel,
following the blasting step; anda decomposing step of decomposing the
residue by exploding the explosive for cleaning in the pressure vessel.

2. The method of cleaning the inside of a pressure vessel for blasting
according to claim 1, wherein the explosive for cleaning is set to a
position separate from the inner wall surface of the pressure vessel in
the setting step.

Description:

TECHNICAL FIELD

[0001]The present invention relates to a method for decomposing a residue
of an object to be blasted such as an explosive material in a pressure
vessel to clean it, following a blasting step of setting the object to be
blasted and an explosive for blasting in the pressure vessel and blasting
the object.

BACKGROUND ART

[0002]There is previously known a method of detonating or bursting an
explosive material to dispose it. Examples of the explosive material
include a military explosive material used for a chemical weapon or the
like (e.g., projectile, bomb, land mine, and naval mine), which
specifically includes a steel shell filled with a burster and a substance
hazardous to a human body, for example. Example of the hazardous
substance can be a chemical agent such as mustard or lewisite toxic to a
human body.

[0003]That blasting method, which does not require disassembling an object
to be treated, is suitable for treatment of the above explosive
materials. This method enables treatment of not only well-preserved
ammunition but also hard-to-disassemble ammunition because of its secular
deterioration or distortion. Further, the explosion generates ultra-high
temperature and pressure which can decompose almost all of the hazardous
substances. This method is, for example, disclosed in Patent Document 1.

[0004]The blasting disposal is frequently performed within a tightly
sealed pressure vessel to prevent a hazardous substance from
outside-leakage or to reduce adverse effects on environment such as
noise, vibration or the like produced by the blasting. The blasting can
generate an off-gas containing a fuel component such as CO, H2 and
CH4 or a residue of the above hazardous substances. The fuel
component or residual hazardous substances contained in the off-gas is
required to be cleaned (detoxified) to a reference value or below before
the discharge of the off-gas to the atmosphere. A bursting disposal of an
explosive material without the above hazardous substances also requires
cleaning a fuel-component thereafter. In addition, the time for cleaning
is desired to be short.

[0005]For the cleaning, conventionally known is a method of neutralizing a
residual substance with an agent, but the neutralization takes a long
time, depending upon the state of the residue. For example, a reaction of
solid residue can require a long time. In the case where the residual
substance is constituted by not a single substance but several
substances, the treatment of it may be required to be separately
conducted several times.

Patent Document 1: Japanese Patent Laid-Open Publication No.

DISCLOSURE OF THE INVENTION

[0006]It is an object of the present invention to provide a method of
cleaning the inside of a pressure vessel for blasting to shorten a
treatment time regardless of the state of residual substances. To
accomplish the object, a method of cleaning the inside of a pressure
vessel for blasting according to the present invention includes: a step
of setting an explosive for cleaning, different from an explosive for
blasting used for an object to be blasted, in an amount necessary for
decomposing a residue of the object inside of a pressure vessel,
following a blasting step of setting the object to be blasted in the
pressure vessel and bursting it therein; and a step of exploding the
explosive for cleaning in the pressure vessel to decompose the residue.

[0007]In this cleaning method, simply setting the explosive for cleaning
inside of the pressure vessel and exploding the set explosive for
cleaning achieve a cleaning treatment in a short time.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 is a sectional view of a pressure vessel used in a method of
cleaning the inside of a pressure vessel for blasting according to the
present invention.

[0009]FIG. 2 is a sectional view of a chemical bomb treated in the
pressure vessel of FIG. 1.

[0010]FIG. 3 is a sectional view showing the cleaning method according to
the present invention.

BEST MODE FOR IMPLEMENTING THE INVENTION

[0011]A method of cleaning the inside of a pressure vessel for blasting
according to the present invention will be below described with reference
to the drawings.

[0012]FIG. 1 shows a pressure vessel 10 for blasting in which a method of
cleaning the inside thereof according to the present invention is
performed. The pressure vessel 10 has a double structure of an outer
vessel 31 and an inner vessel 32. The outer vessel 31 is a strong
pressure vessel made of steel or the like having a sufficient strength to
withstand a pressure produced by blasting an object to be treated. The
inner vessel 32 is made of a strong material such as steel to withstand a
collision with fragments scattered at the time of the blasting.

[0013]The outer vessel 31 is cylindrically formed with both ends in the
axial directions: one of the ends is closed and the other is open. To the
open end is removably attached a removable pressure-resistant lid 11 for
opening and closing the end. Similarly, the inner vessel 32 is
cylindrically formed with both ends in the axial directions: one of the
ends is closed and the other is open. The open end is positioned inside
of the outer vessel 31 so as to face the pressure-resistant lid 11. To
the open end is removably attached a inner lid 33 for opening and closing
the end.

[0014]The inner vessel 32 is not securely fixed but loosely installed
inside of the outer vessel 31 to be allowed to make a slight relative
movement against the outer vessel 31. This loose installation of the
inner vessel 32 protects the outer vessel 31 from direct transmission of
a shock generated by an explosion and the collision with scattered
fragments and prevents an application of an excessive force to the
connection region (fixing region) between the inner vessel 32 and the
outer vessel 31, thereby inhibiting damage in the connection part to
improve the durability of the pressure vessel 10.

[0015]In the inner vessel 32 is performed a blasting disposal of an object
to be blasted such as a chemical bomb, followed by a cleaning process of
a residual substance inside of the pressure vessel 10 by the method
according to the present invention.

[0016]There is a burster tube 111 extending rearward from a head 110,
accommodating a burster (explosive) 112. Inside of the head 110 is
provided with a fuze 113 for bursting the burster 112 in the burster tube
111.

[0017]The burster tube 111 is accommodated in a bomb shell 120, which is
connected to the head 110 and filled with a chemical 121. Attitude
controlling fins 130 are provided at the end of the bomb shell 120
opposite to the head 110 in the axial directions, to control the attitude
of a chemical bomb 100 when it is dropped.

[0018]The burster (explosive) 112 can be a military explosive such as TNT,
a picric acid or RDX. The chemical (hazardous substance) 121 may be, for
example, blister agents such as mustard gas or lewisite, vomiting agents
such as DC or DA, phosgene, sarin, hydrocyanic acid, or the like, whether
liquid or solid.

[0019]The chemical bomb 100 is blasted in the pressure vessel 10 by use of
an explosive for blasting, finally leaving a residual substance in the
pressure vessel 10. The residual substance is to be cleaned according to
the present invention. In detail, as shown in FIG. 1, the chemical bomb
100 surrounded by an explosive 101 for blasting is set into the pressure
vessel 10 by a fixing device (not shown), and thereafter the inner lid 33
and the pressure-resistant lid 11 are attached to the inner vessel 32 and
the outer vessel 31 respectively to enclose the each vessel 32, 31. In
this closed state, a blasting step is performed, wherein the explosive
101 for blasting is blasted by a detonating apparatus (not shown),
thereby blasting the chemical bomb 100. The blasting disposal is
performed once or more times.

[0020]The blasting step leaves a residual substance to be cleaned
according to the present invention in the pressure vessel 10. This
residual substance remains inside of the inner vessel 32 of the pressure
vessel 10 in various forms, depending upon the kind of the chemical bomb
100 or the conditions of blasting followed by the process according to
the present invention. A metal part of the chemical bomb 100, for
example, the head 110, the burster tube 111, the bomb shell 120 and the
posture control blade 130, generally remains as solid metal fragments,
metal powder or the like, while the burster (explosive) 112 and the
chemical agents (hazardous substance) 121 remains as gas, liquid or solid
matter depending on a material in use. If the whole residue or a part of
the residue to be cleaned is a liquid residue A or a solid residue B as
shown in FIG. 3, the residue A or B is positioned near an inner wall
surface 10a of the pressure vessel 10, for example, as is collected on
the bottom or adheres to the inner wall surface 10a. If the whole residue
or a part of the residue to be cleaned is a gaseous residue C, the
residue C diffuses in the pressure vessel 10. In short, the leaving
portion of the residual substance may vary depending upon a phase of the
residual substance.

[0021]The cleaning method according to the present invention enables
decomposing any of the above residual substances. The details thereof are
as follows.

[0022]First, the inner lid 33 and the pressure-resistant lid 11 are
opened, and the above fixing device sets an explosive 1 for cleaning in a
predetermined amount inside of the pressure vessel 10, preferably,
separately from the inner wall surface 10a or more desirably, in the
middle of the pressure vessel 10. The amount of the explosive 1 for
cleaning is determined by analyzing the component and amount of a
residual substance inside of the pressure vessel 10 and calculating an
amount necessary for decomposing the analyzed component to a target value
or below.

[0023]After the set of the explosive 1 for cleaning, the inner lid 33 and
the pressure-resistant lid 11 are closed to tightly seal the pressure
vessel 10, in which blasting disposal is performed. Specifically, the
detonating apparatus detonates the explosive 1 for cleaning. The
explosion causes a propagation of a shock wave. This compresses an air on
the shock wave front to raise a temperature of the air. The shock wave
reaches the inner wall surface 10a of the pressure vessel 10 to raise a
temperature of a combustion gas to approximately 10000° C. or
above by sharply raising the pressure thereof.

[0024]The thus produced high-temperature air and high-temperature
explosive combustion gas have a function of instantaneously decomposing a
substance to be cleaned, whether the substance is gas, liquid or solid
matter. In other words, a residual substance remaining in the pressure
vessel 10 before the performance of the cleaning method can be decomposed
and cleaned in a short time, no matter whether the residue is any of gas,
liquid or solid matter. This function gives a shortened treatment time
regardless of the state of the residue.

[0025]This method is especially effective when the explosive 1 for
cleaning being set in the middle of the pressure vessel 10 separate from
the inner wall surface 10a, as is the case with this embodiment. Setting
the explosive 1 in the middle position as above allows a high-temperature
air and a high-temperature explosive combustion gas to reach each part of
the inner wall surface 10a of the pressure vessel 10 uniformly with less
bias than setting the explosive 1 in contact with the inner wall surface
10a. This makes it possible to effectively decompose any of the above
liquid residue A, solid residue B and gaseous residue C remaining in
mutually different positions, wherever they are left.

[0026]The present invention is however not limited to setting an explosive
for cleaning in the middle of the pressure vessel 10. For example, it may
be set in contact with the inner wall surface 10a of the pressure vessel
10 or in any position apart from the inner wall surface 10a.
Alternatively, in a long pressure vessel extending in the axial
directions, each explosive for cleaning may be set in a plurality of
lengthwise dispersed positions.

[0027]Furthermore, a specific pressure-vessel structure according to the
present invention is not limited to a double structure: for example, a
single or triple structure is also feasible.

[0028]In the blasting step followed by the cleaning process according to
the present invention, the kind of an object to be blasted is not
limited. Although in the above embodiment is blasted a chemical bomb 100
containing burster (explosive) 112 and chemical (hazardous substance)
121, the object to be blasted may lack at least one of the burster 112
and the chemical 121, or may be a container filled with a hazardous
substance such as an organic halogen, for example. A residual substance
produced by blasting the above objects also can be effectively cleaned by
the cleaning method according to the present invention.

[0029]In a blasting step where blasting is repeated several times, the
same kind of object may be blasted in each of the treatments, or a
different kind of object can be blasted in each treatment.

Practical Example

[0030]To verify availability of the present invention, the inventors
actually blasted a chemical bomb obtained by simulating the formation and
explosive amount of the chemical bomb 100 using an explosive for blasting
in the pressure vessel 10, and decomposed a residual substance produced
thereby by exploding the explosive 1 for cleaning in a proper amount.
Table 1 shows components of the residue (before the cleaning) and
components thereof after decomposed (after the cleaning), wherein each
analysis value indicates the concentration of a residual chemical
(hazardous substance) in the gas.

[0031]Table 1 indicates that the residue concentration of dicyanobenzene
(triple bond) is reduced by the cleaning from a high value of 0.02
[mg/m3N] (immediately after blasting the simulated chemical bomb)
before the cleaning to a value lower than 0.005 [mg/m3N], that is,
an analysis value permitting disposal of the residue. On the other hand,
the residue concentration of an oleic acid (double bond), whichever
before or after the cleaning, is below an analysis limit of 0.08
[mg/m3N], which permits disposing of the residue.

[0032]As described so far, the present invention provides a method of
decomposing a residue of an object to be blasted in a pressure vessel to
clean it, following a blasting step of setting the object to be blasted
and an explosive for blasting in the pressure vessel and blasting them
therein. This method includes: a step of setting an explosive for
cleaning, different from the object to be blasted, in an amount necessary
for decomposing the residue of the object inside of the pressure vessel
after the blasting step; and a step of decomposing the residue by
exploding the explosive for cleaning in the pressure vessel.

[0033]This cleaning method achieves the cleaning only by setting the
explosive for cleaning inside of the pressure vessel and exploding the
set explosive for cleaning, thereby shortening the treatment time.
Besides, the residue can be decomposed in a short time, whether it is
gas, liquid or solid matter, in the following way. The explosion of the
explosive for cleaning generates a propagation of a shock wave, which
compresses an air on the shock wave face to raise the temperature. The
shock wave reaches the inner wall surface of the pressure vessel to raise
a temperature of a combustion gas of the explosive for cleaning to
approximately 10000° C. or above by sharply raising the pressure
thereof. This high-temperature air and high-temperature explosive
combustion gas have a function of decomposing the residue in an instant,
no matter whether it is gas, liquid or solid matter, which enables
cleaning the residue in a short time regardless of the state thereof.

[0034]The explosive for cleaning is preferably set apart from the inner
wall surface of the pressure vessel. Setting the explosive for cleaning
in such a position allows a high-temperature air and a high-temperature
explosive combustion gas to reach each part of the inner wall surface of
the pressure vessel uniformly with less bias than setting the explosive
for cleaning in contact with the inner wall surface of the pressure
vessel.